A central problem in neurophysiology concerns the relationship between the inputs to a neuron, the manner of integration of those inputs, and the resulting physiological function. The rabbit retina presents a unique opportunity to study this problem because relatively stereotyped depolarizing or hyperpolarizing bipolar cell inputs to the inner plexiform layer (IPL) give rise to a range of ganglion cell types from simple to very complex. Some complex types, such as direction or orientation selective units, have inputs associated with amacrine cells that have been linked to particular neurotransmitters. These complex ganglion cell types are more frequently encountered in rabbit than in other mammalian retinas. The specific aims of this study are: 1. Structure/function identification -- to determine the morphology of the different physiological ganglion cell classes. 2. Pharmacology -- to determine the specific intracellular effects that result pharmacological alteration of the inputs to each ganglion cell class. 3. Dendritic tree function -- to determine how particular dendritic tree structures are involved in the nonlinear integration of inputs for the extraction of visual information. Intracellular recording provides the only direct and unequivocable method of determining the mophology of physiologically identified cells. The isolated superfused rabbit eyecup preparation permits precise visual stimulation, the necessary stability for intracellular recording and staining, and simultaneous accessibility to pharmacological agents. The proposed study will provide specific information essential to understanding the neural circuitry of the mammalian inner plexiform layer. Since the ganglion cells are the retinal output to the central nervous system, understanding the information processing mechanisms in the inner plexiform layer will contribute not only to our understanding of retinal function, but also to understanding sensory coding and neuronal integrative function in general.